Dynamic Digital Displays, Inc. was established to develop and market a high-performance physician's workstation (the "Voxel Processor"), with improved facilities for interactive three-dimensional (3-D) visualization of human anatomy as derived from CT, MR, or PET scans. Full-scale prototypes which use custom-built computer hardware to generate multi- planar reformatted (MPR) images at 30 images per second, and 3-D views in 1-5 seconds per image, are now fully operational. We have built 4 such prototype systems and have installed one in the Department of Radiation ONcology, Hospital of the University of Pennsylvania, for evaluation. Two more prototype systems are pending installation. We believe these high-performance workstations have unique advantages for Radiation Therapy Planning (RTP), including better tumor and normal tissue localization, the ability to generate any desired view interactively, and simultaneous color-coded presentation of anatomy, target volume and critical structures, beam outlines, and computed dose distribution on any MPR image or 3-D view. Phase I investigations comprised the specification, design and simulation of special features required for RTP. We are now seeking Phase II funding to integrate these features into a commercially viable Voxel Processor based 3-D treatment planning system, which will b brought to market using private sector funding during Phase III.